Conventional devices and systems have been employed for controlling the placement and positioning of selected components on a moving composite web, and for controlling selected processing operations, such as cutting operations. Such systems have been employed to produce absorbent articles, such as disposable diapers, adult incontinence products and feminine care products. The systems have typically tracked the moving web by using time-counts and encoder-counts.
Systems that incorporate electromagnetic radiation shifting indicia have also been employed. The indicia have provided signals which have been used in controlling various processes to be performed on the web, as well as for controlling movement of the web. The indicia have emitted wave-shifted electromagnetic radiation in response to incident radiation of a given range to provide a mechanism for determining the positioning of the web during movement as the processes are performed.
The registration inspection of composite articles during the fabrication of a series of such articles has been accomplished by making a two-dimensional image of a product and analyzing the image to determine the location of a component. The determined location has been compared to a desired location for the component in the composite article, and feedback control signals have been utilized to adjust the fabrication process so that the components will be at the desired locations in subsequent products. When a component is outside of its acceptable position, the article can be removed from the fabrication line without further processing.
Conventional devices and system, such as those described above, have not been sufficiently effective for inspecting the registration and location of component elements on a moving web. The systems have not been sufficiently able to control the registration of process operations and archive the registration data. Many imaging systems have been bulky and have been difficult to use in limited spaces. In addition, the conventional systems have not been sufficiently accurate, particularly when there have been extended distances between the locations of control sensors and the locations of their associated production operations. The systems have been susceptible to errors caused by various factors. Such factors can include, for example, slippage between the moving web and the processing equipment; non-uniform elongations in the web; length-wise oscillations in the web; and vertical vibrations in the web. As a result, poorly positioned or missing elements have still excessively degraded the quality of articles produced from the web, and poor-quality articles have not been efficiently or accurately culled and removed from the production lot. The conventional devices have also not been sufficiently able to automatically adjust the production process and machinery to keep desired parameters within acceptance specifications. As a result, production lines have suffered excessive downtime and reduced production efficiency.